Systems and methods for transporting data across an air interface using reduced address headers

ABSTRACT

Systems and methods are disclosed for transporting data across an air interface using a blending of protocol layers to achieve reduced bandwidth. Advantage is taken of the fact that the extra overhead from, for example, the Ethernet protocol is addressing information pertaining to the destination of the packet. This destination information (for example, the Ethernet address) can be stripped from the transmission prior to the air interface and recreated after the air interface. In one embodiment, the concepts of a proper Layer 2 CS are merged on top of the 802.16 protocol and still retain the benefits of a Layer 2 transparent bridged service layer to the network layer. In one embodiment, the MAC address of the destination is used for the air interface and the Ethernet address is recreated and added on the far side of the air interface.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.13/545,585, filed Jul. 10, 2012; which is a continuation of U.S.application Ser. No. 11/651,238, filed Jan. 9, 2007, now U.S. Pat. No.8,223,771; which is related to and claims priority to ChineseApplication No. 200610162069.x filed Dec. 8, 2006 entitled “SYSTEMS ANDMETHODS FOR TRANSPORTING DATA ACROSS AN AIR INTERFACE USING REDUCEDADDRESS HEADERS”; all of which are hereby incorporated herein byreference.

TECHNICAL FIELD

This invention relates to wireless systems and more particularly to suchsystems having protocols for data transmission and even moreparticularly to systems and methods for transporting data across an airinterface using reduced addressing headers.

BACKGROUND OF THE INVENTION

It has become common place to transport data across air interfaces. Inmost such situations, bandwidth becomes a factor either because a singleuser (such as a PC) is trying to move large data files in a given periodof time or several users are trying to use the same air interface tomove smaller files.

Many data transportation protocols are now in use, some of which dealwith wireline interconnections (such, for example, the 802.3 protocol)and some of which deal with air interface transmissions (such as, forexample, 802.16). These protocols have several layers, including thephysical layer and several operational layers. Each such layer isdesigned to accomplish a certain objective and each such layer requiresa certain format of data. For example, in addition to transportation ofthe payload (typically data), address information must be included as aheader so that the payload can be delivered to the proper destination.In some situations, it is necessary to use additional protocols forspecific purposes. When this is necessary, the additional protocol addsoverhead (data bits) to the communication payload.

One example of the problem is when an Ethernet header is necessary on apacket to deliver the packet to a particular location within, forexample, a local area network. The overhead from the header is not aproblem for those portions of the communication channel (for example,the wireline portions) where bandwidth is essentially unlimited.However, when the communication must pass across an air interface usinga specific protocol, such as, for example, the 802.16 protocol, theaddition of the Ethernet address in the protocol is a burden on the airinterface as it adds bytes (typically 14 bytes). These extra bytes areoverhead to the data being transferred across the air interface and inmany situations is excessive, particularly for low data rate transfers.

One solution to the problem is to carry the IP on top of an IPconvergence sub-layer (IPCS) which would then naturally fall on top ofthe 802.16 frame in Layer 3. The advantage of such an approach is thatit is very efficient because it is IP on top of IP with no additionaloverhead, or very little additional overhead. The downside is that Layer3 is designed to carry network routing data and data loads and thusnetwork administrators are not willing to be impacted by the overhead ofmanaging very large (in terms of data flow) Layer 3 traffic. Such anetwork architecture would be unyielding and difficult to deploy inpractice.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to systems and methods fortransporting data across an air interface using a blending of protocollayers to achieve reduced bandwidth. Advantage is taken of the fact thatthe extra overhead from, for example, the Ethernet protocol isaddressing information pertaining to the destination of the packet. Thisdestination information (for example, the Ethernet address) can bestripped from the transmission prior to the air interface and recreatedafter the air interface. In one embodiment, the concepts of a properLayer 2 CS are merged on top of the 802.16 protocol and still retain thebenefits of a Layer 2 transparent bridged service layer to the networklayer. In one embodiment, the MAC address of the destination is used forthe air interface and the Ethernet address is recreated and added on thefar side of the air interface.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawing, in which:

FIG. 1 shows an example of a local area network based system having anair interface in accordance with the invention;

FIG. 1A illustrates a packet of data moving from a PC across the airinterface to an access router to the network;

FIG. 1B illustrates a packet of data moving from the access router tothe PC across the air interface;

FIG. 2 shows one embodiment of a method for removing headers from airinterface transmission; and

FIG. 3 shows one embodiment for adding headers to air interfacetransmissions.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an example of a local area network based system 10 havingair interface 11 in accordance with the invention. In the illustrativesystem, PC 101 is connected to CPE 102 via high capacity connection 12,which connection can be wireline and could use the 802.3 protocol, ifdesired. CPE 102 is connected to base station 103 via air interface 11.The air interface can use, for example, the 802.16 protocol.

Base station 103 is in turn connected to access router 104 via highbandwidth connection 13 and the router is connected to the network (forexample, the Internet) via connection 14.

The 802.16 protocol used for air interface 11 has two layers (layers 2and 3) over which data can be transported. Layer two is the primary datatransfer layer while layer three handles primarily networkinginformation. Layer two is designed to handle MAC (or IP addresses)addresses and not designed to handle Ethernet addresses. Thus, as shownin FIG. 1A, for data packets having an Ethernet header (such as header113) additional data would have to be embedded in data packet 110. Thus,as it will be seen, the concepts discussed herein will operate to allowdata packet 110 from PC 101 to cross air interface 11 as packet 110′without portion 113. Reconstructed portion 113 (called portion 113′)pertaining to the destination (such as access router 104) is added bybase station 103 on the far side of the air interface to form new datapacket 110″. The information that is carried in the Ethernet header 113′of packet 110″ is the original destination Ethernet address as recreatedby base station 103.

As will be seen, this arrangement is an efficient use of Layer 2 CS,such as IP-CS MAC used on top of 802.16. In essence, then this is aLayer 2.5 protocol for use with 802.16. As will be seen, this layer usesadditional services, such as a proxy function that would be used inconjunction with the IP-CS, as well as a DHCP snooping function tocomplement the IP-CS that is bearing the IP user application traffic.The combination of these features allows the effective appearance of atransparently bridged Layer 2 network from the network administrator andnetwork traffic perspective, yet yields the benefit of a very lowoverhead system by effectively having almost no Layer 2 overhead in thenetwork.

FIG. 1B illustrates a packet of data 120 moving from access router 104to PC 101 across air interface 11. In operation, as will be discussed,data packet 120, which contains data payload 121 and MAC address 122 ofthe destination, has LAN network address (Ethernet header) 123 appendedthereto for delivery to base station 103. Base station 103, in turn,strips header 123 from packet 120′ to form packet 120″ in preparationfor transportation across air interface 11. CPE 102 then addsreconstructed destination (PC 101) Ethernet header 123′ to form packet120′.

One embodiment is operative when the system uses statically configuredaddresses. In such a system, the access router tells the base stationthe Ethernet address information of the destination during theauthentication process. The base station then forwards this information,(such as CPE ID (MAC address) IP, netmask, etc.) to the CPE fortemporary storage thereat. This information then allows the CPE torecreate a destination Ethernet address based on the IP-CS informationthat is part of the MAC address that is not stripped from the datapacket.

Thus, since both the CPE and the base station have the Ethernet addressstored for a given IP CS address, the Ethernet address can be strippedoff and then recreated on the far side of the air interface.

In one embodiment, in the situation of dynamically configured addresses,there is a DHCP helper resident in the CPE. DHCP spoofing is containedin the base station. Thus, when a PC initiates the DHCP process toobtain a network address for a given session both the CPE and the basestation will learn and remember the assigned addresses.

When an ARP request identifying the PC (a request asking where a packetis to be delivered) is found in the base station's look-up table, thebase station will respond as if it were the PC destination. The packetswill then be delivered to the base station, using the base station'saddress and the base station will forward the packet the CPE. The CPE,having the same information in its look-up table as did the basestation, then adds the Ethernet address for delivery to the PC.

When an ARP request identifying a destination comes from the PC, the CPEresponds with its own MAC address. The PC then sends the packets to theMAC address of the CPE. This then eliminates the need for the Ethernetheader in the packet to the base station. The base station then adds theproper Ethernet header because the base station saved the response fromthe DHCP server. The packets will then be delivered to the router inaccordance with the proper Ethernet destination address.

FIG. 2 shows one embodiment 20 of a method for removing headers from airinterface transmission. Process 201 receives a packet for delivery to adestination identified by a header. In some embodiments, the destinationheader will not be attached because the device (such as a base station)will have told the router to use its address and then “knows” where todeliver the packet.

Process 202 determines if the packet is an IP packet or not. If not, thepacket will be discarded by process 206. If it is a packet, then process203 determines if the packet comes from its serving client's list. Ifso, then process 204 removes the destination header and process 205delivers the packet to the air interface.

FIG. 3 shows one embodiment 30 for adding headers to air interfacetransmissions. Process 301 receives packets over the air interface.Process 302 determines if this packet is from a serving client. If not,process 305 discards the packet. If so, then process 303 looks up (orotherwise obtains) the desired destination and process 304 delivers thereceived packet in accordance with information obtained locally (at thereceived end of the air interface).

From the DHCP snooping point of view, the system actually snoops theDHCP packet at both the CPE and base station so that the bridge knowshow to route the IP packets. The system spoofs the MAC address of theCPE which is really the SSID of the device. The subscriber stationidentity has the MAC address format. In this manner the access routerdoesn't know that the bridge is operating in a Layer 3 mode since theoperation appears to be a pure Layer 2 operation across the bridge.

The base station and CPE snooping functions, in one embodiment, resideson both the CPE and the base station. There are, in one embodiment, twosub-group proxy ARP functions. One proxy ARP function resides in thebase station which is a proxy that responds to the access router's downlink request for the location of the destination device matching a givenaddress. The other proxy ARP function resides, in one embodiment, on theCPE side and operates to handle destination request information from thesending device on an uplink request.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method for delivering data packets across anair interface, said method comprising: receiving a data packet at afirst physical location on one side of said air interface, said packethaving a destination location bearing a specific LAN address in additionto its network address, wherein said packet contains said specific LANaddress of said destination location; and transmitting said packetacross said air interface without said specific LAN address, saidspecific LAN address being added at a second physical location to saiddata packet using at least one look-up table keyed to said specific LANaddress; wherein said added LAN address is derived at least in part froman IP convergence sub-layer (IP-CS) information contained in said packetand at least in part from information stored at said second location fordelivering said transmitted packet to said destination location; whereinsaid packet is received across said air interface at said secondphysical location, said destination location determined, at least inpart, from other information contained within said packet and at leastin part from said information stored at said second physical location;and wherein said first physical location removes said LAN address fromsaid packet prior to said transmitting said packet across said airinterface.
 2. The method of claim 1, wherein said first and secondlocations contain transmit and receive ends, respectively, of an airinterface bridge, and wherein said air interface is the 802.16 protocol.3. The method of claim 2, wherein said transmitting of said packet usesat least a portion of a Layer 2 protocol of said bridge.
 4. The methodof claim 1, wherein said at least one look-up table is populated for aparticular session in response to an Address Resolution Protocol (ARP)request from a data packet sending location.
 5. The method of claim 1,wherein said first physical location is a base station.
 6. The method ofclaim 5, wherein said base station includes a dynamic host configurationprotocol spoofing.
 7. The method of claim 1, wherein said secondphysical location is a customer-premises equipment.
 8. The method ofclaim 7, wherein said customer-premises equipment includes a dynamichost configuration protocol helper.
 9. A bridge for use in transportingdata packets across an air interface between equipment located on eitherside of the interface, said data packets deliverable to a destinationlocation based upon the Ethernet address of said destination location,said bridge comprising: means for sending, on a transmit side of saidbridge, each data packet of said data packets across said air interfacewithout the Ethernet address attached to said each data packet; andmeans for controlling, on a receive side of said bridge, the delivery toa proper destination of said data packets arriving without the Ethernetaddresses attached thereto; wherein said means for sending said eachdata packet and said means for controlling the delivery are on differentsides of said air interface; wherein said means for sending comprises:means for removing the Ethernet address from said each data packet priorto said sending, wherein said each data packet contains the Ethernetaddress prior to removal; wherein said controlling means comprises:means for adding the Ethernet address of said destination location toreceived ones of said data packets using at least one look-up tablekeyed to the Ethernet address, wherein said means for adding comprisesat least one look-up table for determining the Ethernet address based onIP-CS information contained in said received ones of said data packets,said look-up table keyed to the Ethernet address is populated for aparticular session in response to an Address Resolution Protocol (ARP)request from a data packet sending location.
 10. The bridge of claim 9,wherein said air interface is the 802.16 protocol.
 11. The bridge ofclaim 10, wherein said means for sending comprises: means for using atleast a portion of a Layer 2 protocol of said bridge.
 12. The bridge ofclaim 9, wherein said transmit side of said bridge is a base station.13. The bridge of claim 9, wherein said receive side of said bridge is acustomer-remises equipment.
 14. A method of operating a bridge fortransporting data packets across an air interface between equipmentlocated on either side of the interface, said data packets deliverableto a destination location based upon the Ethernet address of saiddestination location, said method comprising: sending, from a transmitside of said bridge, each data packet of said data packets across saidair interface without the Ethernet address attached to said each datapacket, wherein said each data packet includes the Ethernet addressprior to sending and the Ethernet address is removed from said each datapacket prior to said sending; controlling, at a receive side of saidbridge, delivery to a proper destination of said data packets arrivingwithout the Ethernet addresses attached thereto; and adding, at saidreceive side of said bridge, the Ethernet address of said destinationlocation to received ones of said data packets using at least onelook-up table keyed to the Ethernet address, wherein said addingcomprises determining the Ethernet address based on IP-CS informationcontained in said received ones of said data packets and using at leastone look-up table keyed to said IP-CS information.
 15. The method ofclaim 14, wherein said air interface is the 802.16 protocol.
 16. Themethod of claim 15, wherein said sending comprises: using at least aportion of a Layer 2 protocol of said bridge.
 17. The method of claim14, wherein said look-up table keyed to the Ethernet address ispopulated for a particular session in response to an Address ResolutionProtocol (ARP) request from a data packet sending location.
 18. Themethod of claim 14, wherein said sending comprises: adding to said eachdata packet address information, other than the Ethernet address,pertaining to said destination location of said each data packet, saidadded information being determined by said transmit side of said bridge.19. The method of claim 14, wherein said transmit side of said bridge isa base station.
 20. The method of claim 14, wherein said receive side ofsaid bridge is a customer-premises equipment.